Medical tube assemblies such as employed in or used as catheters, fluid transfer tubes and the like, generally use a tube fitting with a luer connector at one end for connecting the tube or catheter to another fluid device in a fluid system.
The tube and fitting obviously should be so connected together that they do not separate or result in fluid leakage under mechanical pulling forces and fluid pressures that may be encountered when the assembly is in use. However, such failures have been encountered, especially when the tube and fitting are of a relatively small size.
One method of connecting the tube and fitting together is to provide the fitting with a recess or bore and solvent bond the outer surface of one end of the tube to the walls of the recess. With such an assembly, however, any separating forces or pulling force on the catheter encountered when in use tends to narrow the catheter, resulting in inward forces tending to pull the catheter inwardly away from the recess walls. Such connections have not been entirely satisfactory, especially where the tube is of small diameter. Also, the solvent generally weakens the catheter and fitting at the connection. Furthermore, with such a method the inner diameter of the recess and the outer diameter of the tube must be held to close tolerances, further complicating the manufacture of such an assembly.
Another method employed is to bond the inner surface of one end portion of a tube to the outer surface of a hollow pin. With this method, the solvent tends to weaken the walls of both the pin and the tube, resulting in a weak connection between the fitting and tube, especially where the tube and pin are of relatively small diameters and the wall thicknesses of the pin and tube are small.
The use of solvents and adhesives in obtaining a fluid-tight connection between a tube and fitting also has the disadvantages of producing fumes and odors, and such materials are not easily employed and must be stored.